A cannula is a hollow flexible tube used in medicine to introduce or open a lumen or to insert medical devices and can be introduced into the human body over a guidewire. Typically this guidewire is a highly-flexible metal coiled wire less than 0.5 mm in diameter and is used extensively in cardiovascular medicine. A catheter has very low flexural rigidity but is able to be pushed from the vein in the leg all the way through the heart. A guidewire can be inserted into the body of a patient in a generally conventional manner and advanced to a desired location where a biopsy of cells and tissue is to be taken. The process of advancing the guidewire can be done purely by exercising the touch and feel of an experienced physician, or can be carried out with visualization technologies, such as fluoroscopy, X-ray or computed tomography (CT) imaging, magnetic resonance imaging (MRI), ultrasound imaging, optical tomography, etc. Clearly, it would be desirable to advance a device that serves as a guidewire by imaging the lumen in the body of a patient through which the device is being advanced.
Catheters with cannula tools that are introduced into a patient's body by means of slipping the catheter with its cannula tools over a guidewire that has previously been maneuvered to a desired location in the body are well developed for cardiovascular applications. In these applications, the task of taking a biopsy for disease diagnosis was not required, so tools for cell sampling have not previously been developed. In contrast, one of the primary purposes of endoscopy and bronchoscopy is disease diagnosis, which often requires taking cell samples and tissue biopsies. It is likely that appropriate tools for taking cell and tissue samples will be useful in the endoscopy and bronchoscopy fields, along with urology and other medical fields that require cell sampling for disease diagnosis. It would clearly be desirable to develop a variety of different types of guidewire-based tools for use in collecting samples from an internal site in a patient's body for cytopathological diagnosis, so that these tools can be advanced over a guidewire that has imaging capability.
After a guidewire has been inserted and advanced to a desired site, it would further be desirable to introduce a multifunction tool over the guidewire as a cannula, or otherwise couple the tool to the guidewire so that it can be advanced to the site over the guidewire and be employed to obtain a biopsy sample at the site. It would also be desirable to develop multifunctional cannula tools that can be employed to carry out more than one function, for example, dislodging cells and tissue, and then capturing and withdrawing the cells and tissue for diagnostic evaluation, to detect disease by applying conventional cytological and pathological procedures.
An endoscope can be made that has only a single optical fiber, for example, 0.1 to 0.3 mm in diameter. Typically, optical fibers made from fused silica, silicon-dioxide, or quartz have the ability to withstand compressive forces and can be used in a way similar to a catheter guidewire, since the distal tip can be steered, e.g., by bending it as it is advanced through a body lumen. Accordingly, it would be desirable to provide a “guidewire with eyes” for introducing cannula tools to a treatment site within a patient's body. Such a device should have many more uses than as a simple guidewire or catheter, since the ability to image as the device is being advanced (and while it is being withdrawn) through a lumen would enable a medical practitioner to introduce the cannula tools to a desired site without the need for external imaging. Such a device would enable cannula tools to be introduced for many different medical applications, and to be used more effectively at a desired site by providing a visual image showing the medical practitioner what is occurring as the cannula tools are being used.